The return of an old pestilence?

Smallpox occupies an important place in the history of infectious disease in the world. For hundreds of years the disease was one of the most dreaded, lethal and most common of all infectious diseases.

During the 19th century the disease killed at least 400,000 people annually in Europe. As late as the 1950s it is estimated that 50 million cases of the disease occurred every year throughout the world. Australia did not escape from this rampage and between 1789 and 1917 there were at least 15 outbreaks of the disease.

The last smallpox epidemic to occur affected a large part of New South Wales between 1913 and 1917 causing at least 3,000 cases. In this case it was a very mild form of the disease (variola minor) with a low infectivity rate. Most of those affected developed a mild illness with far less scaring than was usually associated with smallpox. Only four people are recorded as dying from the disease during this outbreak.

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Although the WHO declared smallpox to have been eradicated from the world in December 1979 over the last 25 years there has remained considerable speculation about the possible use of the smallpox virus as a bioterrorist weapon.

Citing rumours that a rogue nation or terrorist groups may have accessed secret stores of smallpox virus, the USA and Russia retained stocks of the virus frozen in liquid nitrogen ostensibly to develop improved vaccines. Some believe that it is only a matter of time before smallpox is covertly released in a bioterrorist attack.

Be that as it may, are we now possibly facing a resurgence of smallpox brought about by global warming.

The effects of global warming on our health have usually focused on the human impact of heat waves, droughts, floods, bushfires as well as influencing the breeding cycle and geographical distribution of disease vectors such as mosquitoes. Now evidence has emerged from the northern most parts of Siberia that suggest something even more threatening.

As global warming continues and unusually high temperatures are melting the permafrost in the frozen north of Siberia, it remains possible that a range of viruses might be liberated.

Already there is evidence that anthrax spores have been released and more than 20 local people have been hospitalised with the disease. In the early 20th century anthrax killed thousands of reindeer and local cattle all of which were hastily buried locally and until recently their graves have remained undisturbed.

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Now the thawing of the ice is bringing to the surface many of the corpses of the buried animals and it is more than possible that the soil is saturated with anthrax spores.

This follows an earlier incident when in 1979 in Sverdlovsk a major outbreak of anthrax followed an explosion in a research compound where animals were kept presumably to research anthrax. Up to 1,000 people subsequently died from anthrax.